1. Field of the Invention
The present invention relates to display apparatus for displaying an image with a display device such as an electron-emitting device, an electroluminescent (EL) device, an LED device, a plasma light-emitting device, and a liquid crystal device, and to a method of driving the display apparatus.
Specifically, the invention relates to a multiplexing drive method for a matrix display with a plurality of self-luminous display devices arranged to form a matrix pattern.
2. Related Background Art
The above plural display devices control, to display images, signals that are to be supplied to a matrix wiring consisting of a plurality of row-directional wirings (scanning wirings) and a plurality of column-directional wirings (modulation wirings).
Hereinafter matrix displays are described taking as an example a self-luminous display that uses light emitted from a phosphor to form an image.
In this type of displays, energy of particles emitted from an electron-emitting device or the like is utilized to excite a phosphor. The brightness of the obtained light varies depending on to what degree the phosphor is excited and/or how long it is excited.
Such display apparatus is disclosed in, for example, Japanese Patent Application Laid-Open No. 07-235256 (U.S. Pat. No. 6,313,571), Japanese Patent Application Laid-Open No. 08-45415, Japanese Patent Application Laid-Open No. 2000-29425 (European Patent No. 936,596), and Japanese Patent Application Laid-Open No. 08-248920.
FIG. 76A shows an example of drive signals for driving a conventional display and FIG. 76B shows a display state of a 3 rows×3 columns matrix display using these drive signals.
Here, one vertical scanning period for displaying one frame of image consists of three horizontal scanning periods, and Sy1, Sy2, and Sy3 each represents a scan signal supplied to a scanning wiring. Here, a horizontal scanning period is a selection period in which a negative voltage is applied in each scanning wiring, and all the scanning wirings have the same length of selection period.
Sx1, Sx2, and Sx3 each represents a modulation signal (data signal) supplied to a modulation wiring. In the example shown here, the modulation signals are of pulse width modulation system in which the pulse width is modulated in accordance with the luminance level (gradation) of a pixel. The modulation signal Sx1 represents signals with which the luminance levels to be obtained are 1, 1, and 3, and which are supplied in time series to a modulation wiring. Similarly, the modulation signal Sx2 represents signals with which the luminance levels to be obtained are 1, 2, and 2, and the modulation signal Sx3 represents signals with which the luminance levels to be obtained are 1, 1, and 1.
In this way, the scanning wirings are selected one at a time to set the luminance for each of the three pixels on the selected row in each horizontal scanning period. Here, the pixel on Low 3, Column 1 is given a luminance level of 3 and emits the brightest light.
Generally speaking, display apparatus with bright screens are preferred to those with less bright ones. When an overall dark image includes some bright spots, in particular, it is desirable if display apparatus can give the bright spots a far higher luminance (peak luminance) compared to the luminance of the dark part of the image in order to display the details of the dark part with good image quality.
However, in display apparatus of so-called line sequential scanning that employs time division to select scanning wirings one at a time as described above, the maximum light emission time of each pixel generally cannot exceed the length of selection period within a horizontal scanning period and the display luminance of the display apparatus is accordingly limited.
Furthermore, a period in which a scan selection signal is applied but a modulation signal is not applied is wasteful, except a blanking period necessary for other processing, since a voltage is applied to a scanning wiring in this period yet it does not contribute to light emission of pixels.